Process of converting white lead into oil-paste.



GUSTAV BISCHOF, OF LONDON, ENGLAND.

PROCESS OF CONVERTING WHITE LEAD INTO OIL-PASTE.

SPECIFICATION forming part of Letters Patent NO. 654,088, dated July 17, 1900.

Application filed arch 26, 1900. Serial No. 10,268. (No specimens.)

To all whom it may concern:

Be it known that I, GUSTAV BIsoHoF, a citizen ofEngland,residing at Hythe road,Willes den Junction, London, in the county of MiddleseX, England, have invented a certain new and useful Improved Process of Converting White Lead into Oil-Paste, (for which I have applied for a patent in Great Britain, dated February 12, 1900, No. 2,774,) of which the following is a specification.

The white lead obtained as described in the specification to my Patent No. 442,943 contains water, acetic acid, and sometimes sugar.

My present invention consists in a process for converting such white lead into a marketable oil-paste or ground white lead without previous drying of the white lead, which is an operation very dangerous to the health of the operatives. For this purpose the white lead is in the first instance pressed and Washed free from liquor in a filter-press, as is usual, 1

previous to drying. The press-cakes thus obtained still contain a certain proportion of Water, which has to be removed. In order to effect this, the press-cakes are mixed with oil and subjected to a churning operation in a suitable pug-mill. The oil combines with the white lead and the water is set free. It is, however, difficult to effect this economically within a reasonable time unless such an excess of oil is added that the resulting paste becomes too thin for the market, being, in fact, in the condition of a paint and not of a paste, which should contain only about eight or ten per cent. of oil. Moreover, the oil employed must not be boiled oil, which would cause the paint to harden in keeping, and such a paint would be objectionable, as it would not dry well.

Now in order to avoid the difficulties and objections arising from employing a large quantity of oil I effect the mixture of the white lead and oil in the following manner: About one-third part of the whole charge of press-cake is in the first instance mixed in the pug-mill with about two-thirds of the total oil required to form the charge into a marketable paste. While the excess of oil facilitates the same pug-mill, adding to the blade-surface, thus increasing the resistance and causing the particles of white lead and oil to agglomerate more readily until a cake begins to be formed, when I again reduce the surface of the agitating-blades either in the same or in another pug-mill. The Water, Which is soon separated, is then run off and the rest of the press-cake and of the oil is gradually added, while the pugging goes on until the whole is thoroughly incorporated. I then effect the dry-ing of the cake-"that is, the removal of the mechanically-adhering water-by direct ing a current of hot air onto the material while it is being pugged, taking care that the heat does not rise so high as to overheat or discolor the white lead.

Having thus described the nature of this invention and the best means I know of carrying the same into practical effect, I claim- The herein-described processof converting white lead into oil-paste, the said process consisting of the following steps of operation upon the crude material: filter-pressing and Washing, pugging about one-third part of the white lead with about two-thirds of the oil, running off separated water, pugging in the remainder of the white lead and oil, drying by a current of hot air directed over the surface of the material while it is pugged.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

GUSTAV BISOHOF.

Witnesses:

GERALD L. SMITH, EDWARD GARDNER. 

